Conversion of liquid to solid tetrachlorobutane



July 10, 1951 K. c. EBERLY 2,560,019

CONVERSION oF LIQUIDs To SOLID TETRACHLOROBUTANE Filed Nov. 22, 1947 A ttarneys Patented July 10, 1951 CONVERSION OF LIQUID TO SOLID TETRACHLOROBUTAN E Kenneth C. Eberly, Akron, Ohio, assignor to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio Application November 22,1947, Serial No. 787,505

3 Claims.

This invention relates to a process for converting the liquid modification of 1,2,3,4tetrachloro butane to the solid modification thereof.

123,4-tetrachlorobutane (hereinafter designated tetrachlorobutane contains two symmettrically disposed a symmetrical carbon atoms (positions 2 and 3) and therefore occurs as a mesomodiiication and as an (unresolved) dlemixture. One of these modifications (hereinafter designated the solid modification) melts at about 72 C., while the other (hereinafter designated the liquid modilication) freezes only at very much lower temperatures. The solid modification is the more desirable one, since it may be purified by recrystallization. Further, the solid modification, upon dehydrohalogenation by means of caustic, gives much higher and purer yields of 2,3-dichlorobutadiene than does the liquid modification.

In the synthesis of tetrachlorobutane, for instance by chlorination of butadiene, the production ci a certain amount of the liquid modification is unavoidable. By the proper choice of conditions, catalysts, etc., the yield of the solid modificaticn may be increased. In practical operation, however, at least 30% of the tetrachlorobutanes obtained will usually consist of the liquid modification, which must be discarded or diverted to the manufacture of relatively less pure products.

Accordingly, it is an object of this invention to convert the liquid modification of tetrachlorobutane to the solid modification.

Another object is to convert the liquid modification to the solid by a process which may be carried out continuously.

A further object is to provide such a process which may be carried out expeditiously and economically in readily and cheaply procurable equipment, with a minimum of skilled supervision.

SYNOPSIS OF THE INVENTION It has been discovered by this invention that the liquid modification of tetrachlorobutane, when subjected in the vapor phase to temperatures in the range 100 C.-525 C., becomes partly converted to the solid modiiication. The reaction appears to be one of equilibrium, slightly favoring the solid modification, and in order to increase the yield of solid modification, the process may be carried out cyclically, the solid modification being separated from the reaction products and the liquid being recycled. The reaction may be accelerated by the presence of catalysts, such as surface catalysts, and particularly by the action of zinc chloride supported on porous carriers. The reaction is also more rapid in the higher temperature ranges, in which ranges, however, there come into play competing reactions such as cracking and carbonization, which result in a net loss of materials.

TEMPERATURE OF OPERATION As noted, the temperature of operation may vary from C. to 525 C. Below this range, the reaction becomes impractically slow, While above this range the loss of materials by way of cracking, polymerization, etc., is excessive. Between these limits, the choice of temperature de' pends upon an economic balance of speed of ren action and consequent charges for reactor space on the one hand and cost of lost material on the. other hand. The upper portion of the temperature range is also somewhat less desirable due to corrosion and fouling of the equipment which sets in at these ranges. In general, provided no catalysts are employed, the economically most ad- Vantageous temperatures lie between 300 C. and 450 C. If there is employed a carrier-supported zinc chloride catalyst as described below, the most advantageous range will be somewhat lower, say in the range C`.250 C.

THE RATE OF REACTION AND DWELL OF MATERIALS IN THE REACTION ZONE As noted above, the reaction to which the instant invention relates is reversible, and comes to an equilibrium in which the solid form of tetrachlorobutane predominates to some extent. HOW- ever, the order of the reaction appears t0 be such that, after more than about 25% of the liquid modification of tetrachlorobutane has been converted to the solid, further approach to the equilibrium conditions becomes unprotably slow, particularly if conditions are sufficiently drastic that competing reactions such as carbonization and cracking are appreciable. In general, it will not be advantageous to press the reaction beyond a yield of about 25% of solid in a single treatment of the liquid modification feed stock. This yield corresponds to a minimum feed of at least .0002 gram of liquid tetrachlorobutane per cubic centimeter of reaction space per hour. A feed of greater than 0.1 gram of liquid tetrachlorobutane per cubic centimeter of reaction space per hour will result in rather low percentage of conversion.

The relatively louT conversion obtained on a single pass of the feed stock may be offset, in accordance with this invention, by separating the liquid and solid modiiications from the product leaving the reaction zone, and recycling the liquid modification back to the reaction zone. The same result may be obtained by forwarding the unconverted liquid modication to a second conversion treatment zone, again separating the liquid from the solid modication, rie-forwarding the unconverted liquid, and so on, limited only by the economic balance between recovery of solid modication and cost of the additional treatments.

.4 production with recycling of the unconverted liquid modication.

In the description to follow, all parts given are by weight.

Another limitation on recycling and retreatmentA 5 EXAMPLE I of the uiiconverted liquid is the accumulation, in the system, of cracked products, and of impurities Variation .of conditions and Optimum introduced with the initial feed. This limitation values thereof can be overcome, to a considerable extent, byA purging the impurities from the recycled or re` l0 The apparatus employed in this example is treated liquid material. The separation of the Shownin Fig` 1 as Comprising a 22 mm, (outside Solid modioation at eaeh Stagemay be aCCOmdiameter) borosilicate glass reaction tube I0 phshed by freezmg out, or by distiatlon. Inseriplaced in an electric tube furnace l2, the heating eral, recycling and/0r forwarding 0f the llquld zone being 69 cm. long. The charging end la is modification as above outlined may be carried l5 bent; upwarmy, and a, dropping funnel I6 fitted out profitably t0 e degree SUiCh aS t0 Obtain 91 thereinto through a neoprene stopper I8. The 60% overall yield Of SOld mOdCatOn 0f tetradischarge end 20 is directed into a condenser 22 chlorobutane product. On the basis o f 2.0% oo nand receiver 24. A vacuum connection 25 is proversmn m a Smale reaction stage, this 1s equivvided for maintaining the system under a vacalent t0 about 4 theOretlCal StageS- 20 uuin. A series of thermocouples 26 is provided for determining and regulating the temperatures CATALYSIS at the various points along the tube.

. A number of runs was made in this a aratus, As above noted, the conversion of solid to liquid using various temperatures rates of fd and tetrachlorobutene may be greatly eecelera'ted by 25 catalysts inthe reaction tube I0. In eachcase, the use of e supportee Zine Chlerlde eete'lyst the temperature of the tube IG was adjusted to Simple Surface catalysis. Such es .prevlded by the value selected for that run, and the system perells messes sueh as Smee gel ectlve eleys ete' evacuated to 10D-159 mm. to facilitate vaporisa- 'provlde e cereal amoene of eetelytle effect' tion of the material fed. Substantially pure liq- Hewevelg the moet effective catalyst found Cem' 30 uid modication of tetrachlorobutane,l to the expnses 2me fehlende Supeoeted upm? a Smteble tent of 100 grams, was charged into the dropping porous carrier such as silica gel, diatomaceous funnel m and dropped into the tube In at the earth' active clay ,pumlee or the, hke' '11h15 preselected rate, whereby it became vaporized catalyst roughly shifts the conversion react1on in the tube m, subjected to the heat prevailing condltlons downward by @out 100' C- (L e 35 therein, and discharged and condensed in the Speeds up thedeslred remmen to a rate approxi condenser 22 and receiver 24. When all the mamately what 1t would be without a catalyst but teral in the dropping funnel I6 had been used at a temperature 100, C- hgh than the tem" up, the product collected at 24 was fractionally Denture actually employed Wlth the Catalyst) distiiied. The fraction, if any, coming over be- Without greatlyl accelerating the competing re- 40 10W 130 Q at 100 mm pressure was discarded actions of cracking etc. I n as consisting of cracked products. The remain- With the foreeome genera-1 dlsleusslon 1n mmd, der, consisting or solid and liquid tetracnlorobuthe invention will now be described in detail in tane, was redistmed through a, Column at 22 mm connection with the attached drawings, inwhich: pressure. The fraction coming over at 93.0-94-5 Fig- 1 ShOWS an apparatus fOr demonstrating 45 C. was substantially pure liquid tetrachlorobuthe variations of which the .instant invention is tane, and the residue was substantially pure solid capable, and tetrachlorobutane. Set forth herewith in Table I Fig. 2 shows an arrangement for continuous are the particulars of the several runs.

Table I Reaction Conditions Products (Percent of Material Charged) Condition of Fl R te anliel'llsutbe 0W a f Lossesin sexie Liquid C t l t Temp. (gm.C4H5Q1i) at End of Total Matl F C k d CH C1 CH C1 R N a a 0 @i weeg Re Recovered eletti.) e Rate Raat n 221 .oo-13 e7 s 1.7 1.7 1 24o .01115 99 1 0.o 2.9 2 sos .co1 es 32 o. o 5. 1 a 325 99 1 2.1 1.7 4 35(2) 0005 ge e 51' g Non@ 421 10013 97 3 7 c 11 1 7 44o .01104 97 3 c. e s. 1 s 457 .0017 o2 1 7.3 8.1 9 .0005 s1 19 14. 2 17. s 1o 47s .0043 99 1 4. 6 3. 7 11 523 .co1 4s 52 25. e li. 1 12 23o co1?, 91 9 o. 3 2. 5 13 silica Gei(Note1 30o .0011 9s 7 2.o 7.o 14 ses A11013 72 2s s. c 11. 9 15 9o .co4 s2 (note s) 1s o o 0.o 1e Si1caGelandl0% 194. .001 86 (note 3) 14 0.4 10.1 17 znoii (Note 2). 231i` .co1 85 (nete s) 15 .5 17.7 1s 281 .co1 so (note 3) 2o 4.o l 5.4 19

NOTE l. 86 grains of 6-20 mesh silica gel packed into heating section oi the tube l0. n

NOTE 2. 86 grains of 6-20 mesh silica gel impregnated by means of an aqueous solution With 10% by Wieght of the silica gel of zinc chloride thoroughly dried before use at 225 C. packed as in note l.

NOTE 3. The loss in these runs is due largely to hold-up inthe catalyst mass at the end of the run.

EXAMPLE II Continuous operation-Recycle of unconverted tetrachlorobutane The equipment employed in this example is shown in Fig. 2 as comprising a supply tank 30 containing the liquid tetrachlorobutane to be converted to the solid form, which supply tank feeds through a throttled line 3i into an evaporator 32 containing a heating coil 34 for vaporizing the liquid tetrachlorobutane into the rest of the system. The vaporized tetrachlorobutane passes through a line 36 to a series of three vertical steel reactor tubes 38, each 6 inches in diameter and 7 feet tall, connected in series. The tubes are packed as indicated at i0 with the silica gel catalyst referred to in note 2, Table I, and are provided with electric heater 42. The tubes are maintained at 220 C., 150 mm. pressure, and throughput is at the rate of .001 gram of tetrachlorobutane per c. c. of reaction space per houri. e., the conditions of item 18 of Table I are simulated as far as DOs sible. Passage through the tubes 38 effects the conversion of about of the liquid tetrachlorobutane to the solid modication. The tubes 38 discharge vapors of the mixed liquid and solid modifications at M into the feed section of a reflux tower 45 packed with vertically disposed glass bers and providing an equivalent of 20 plates above and below feed under the conditions of operation, the reflux ratio being 0.8:1 (reiiux: vapors from top of tower), still head temperature being 132 C., still bottom 142 C., pressure at still head being 100 mm. The solid modication is discharged at the reboiler section 43, while the liquid modification passes out through a partial condenser 48 to the feed section of a stripper column 50. The stripper column is operated so as to purge out, as overhead, a quantity of material equal to about 30% of the feed at 3l, thus continuously purging the system of cracked products and casual impurities along, of course, with an unavoidable loss of some tetrachlorobutane constituents.

The liquid tetrachlorobutane discharged from the reboiler 52 is recycled at 53 to the vaporizer 32. In continuous operation, the above equipment effected between about 50% and about 65% conversion of the liquid tetrachlorobutane supplied at 30 to solid tetrachlorobutane discharged at 46.

Reference is made to the companion application of Eberly and Reid, Ser. No. 787,504, iled November 22, 1949, which is directed to the use specically of the zinc chloride catalyst.

What is claimed is: y l

1. Process which comprises heating the liquid modification of 1,2,3,4-tetrachlorobutane at temperatures between 300 C. and 450 C., whereby to convert a portion of the liquid modication of 1,2,3,4tetrachlorobutane to the solid modification, and separating the solid modification of 1,2,3,4-tetrachlorobutane from the resultant mixture.

2. Process which comprises heating the liquid modification of 1,2,3,4-tetrachlorobutane at temperatures between 300 C. and 450 C. whereby to convert a portion of the liquid modification of 1,2,3,4-tetrachlorobutane to the solid modication, separating the solid modification of 1,2,3,4 tetrachlorobutane from the resultant mixture, heating the residual liquid modification of 1,2,3,4 tetrachlorobutane at temperatures between 300 C. and 450 C. whereby to convert a further portion of the liquid modification of 1,2,3,4tetra chlorobutane to the solid modification, and separating the newly formed solid modification of 1,2,3,4-tetrachlorobutane from the still unconverted liquid modification of 1,2,3,4tetrachloro butane.

3. Continuous process of converting the liquid modication of 1,2,3,4tetrachlorobutane to the solid modication, which comprises passing the liquid modification through a reaction zonek maintained at from 300 C. and 450 C. whereby to convert a portion of the liquid modication, to the solid modification, separating the solid modification from the resultant mixture, and recycling the residual liquid modification to said reaction zone.

KENNETH C. EBERLY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,038,593 Muskat Apr. 28, 1936 2,422,252 Otto June 17, 1947 OTHER REFERENCES Jacobson: Jour. Am. Chem. Soc, vol. 54, pages 1545-8 (1932).

Backer et al.: Rec Trav. Chim. des Pays-Bas, Vol. 54, pages 52-6 (1935) Betti et al.: Atti X congr. intern. chim., vol. 2, pages 112-16 (1938). 

1. PROCESS WHICH COMPRISES HEATING THE LIQUID MODIFICATION OF 1,2,3,4-TETRACHLOROBUTANE AT TEMPERATURES BETWEEN 300* C. AND 450* C., WHEREBY TO CONVERT A PORTION OF THE LIQUID MODIFICATION OF 1,2,3,4-TETRACHLOROBUTANE TO THE SOLID MODIFICATION, AND SEPARATING THE SOLID MODIFICATION OF 1,2,3,4-TETRACHLOROBUTANE FROM THE RESULTANT MIXTURE. 